Increase in leaf temperature opens stomata and decouples net photosynthesis from stomatal conductance in Pinus taeda and Populus deltoides x nigra.

Josef Urban,Miles W Ingwers,Robert O Teskey,Mary Anne Mcguire

doi:10.1093/jxb/erx052

Abstract

The effect of temperature on stomatal conductance (gs) and corresponding gas exchange parameters was studied in two tree species with contrasting leaf anatomy and ecophysiology-a broadleaf angiosperm, Populus deltoides x nigra (poplar), and a needle-leaf gymnosperm, Pinus taeda (loblolly pine). Experiments were conducted in growth chambers across a leaf temperature range of 19-48°C. Manipulations of temperature were done in well-watered and drought soil conditions and under ambient (400 ppm) and elevated (800 ppm) air CO2 concentrations. Increases in leaf temperature caused stomatal opening at both ambient and elevated [CO2]. The gs increased by 42% in poplar and by 40% in loblolly pine when leaf temperature increased from 30°C to 40°C at a vapour pressure difference of 1 kPa. Stomatal limitation to photosynthesis decreased in elevated temperature in loblolly pine but not in poplar. The ratio of net photosynthesis to gs depended on leaf temperature, especially at high temperatures. Evaporative cooling of transpiring leaves resulted in reductions in leaf temperature up to 9°C in well-watered poplar but only 1°C in drought-stressed poplar and in loblolly pine. As global mean temperatures rise and temperature extremes become more frequent and severe, understanding the effect of temperature on gs, and modelling that relationship, will become increasingly important.

Highlights

Plant stomata play a key role in water and carbon cycles
Under unlimited soil water availability, when leaf temperature increased from 30 °C to 40 °C, gs increased by 42 % in poplar and by 40 % in loblolly pine, at a vapor pressure difference (VPD) of 1 kPa and [CO2] of 400 μmol mol-1 (Fig. 1a, d; Table S1; p < 0.001)
Increasing the [CO2] from 400 to 800 μmol mol-1 caused partial stomatal closure, which was more pronounced in poplar than in loblolly pine

Summary

Introduction

Plant stomata play a key role in water and carbon cycles. Most water moving from terrestrial ecosystems into the atmosphere passes through plants and the precise amount is regulated by stomata. Stomatal conductance (gs) is a key factor determining the rate of net photosynthesis and, the global carbon cycle and plant carbon metabolism. Stomatal regulation is one of the main factors which determine local growth and survival of plants and global cycles of mass and energy. The conditions in which plants grow are changing and we still do not know enough about plant stomatal regulation to predict future stomatal responses of plant species and their effects at ecosystem and global scales (Lin et al, 2015)

Methods

Results

Discussion

Conclusion